Study On Fuel Cell Hybrid Power System Used In Electric Vehicles

Energy crisis and environmental pollution are two major problems that human being has to solve.These two problems push the traditional vehicle’s power system is developing forward to a cleaner and higher efficient requirement,and the proton exchange membrane fuel cell(PEMFC)hybrid power system is a new and application prospect for the motive energy.Based on the PEMFC + lithium battery hybrid electric vehicles(HEV),the system’s composition and operating principle of the PEMFC are analyzed firstly,and the HEV components’ parameters are optimized and matched.Then,two control stratagies of the Rule-Based and ECMS are used to achieve an optimal control of the power split ratio,and consequantly to protect the PEMFC,battery and improve system efficiency.Finally,some typical topologies and operating theory for the hybrid power system are analyzed,and the analysis results are verified by experiments.Firstly,in view of the PEMFC.Its stack and auxiliary components are analyzed.Based on its operating theory,a simulation model is created,and the impacts on the PEMFC performance due to the air intake flow rate and the stack output current are emphasized.Secondly,thehybrid power system topology of PEMFC and lithium batteries is designed.The parameters of the HEV are optimized and matched,and the HEV is constructed based on the topology.Then the mathematical models and simulation models corresponding to lithium batteries and DC/DC converter are created,and their performance and efficiency characteristics are analyzed.Based on this,thecontrol algorithm for vehicle power split ratio optimization based on two control strategies,Rule-Based and ECMS is designed.Then based on UDDS operating conditions,the feasibility of the two control algorithms was verified by simulation.Finally,The topology and energy flow of several typical electro-hydraulic hybrid systems are analysised.A double closed-loop control strategy of feed forward(FF)and feed back(FB)is designed to improve the DC/DC converter’s response speed and tracking accuracy of current/voltage.Then an experimental bench is build for experimental verification.